Recent studies suggest that a dimensional, hierarchical model of mental disorders has clear advantages over a categorical nosology. It appears that such a model is better able to account for the excessive diagnostic comorbidity, poor diagnostic stability, and weak reliability observed in many psychological disorders. However, before a quantitative model can be applied to a subsequent edition of the DSM, it must be broadened and refined. Specifically, more disorders need to be included in structural analyses of psychopathology because the majority of DSM diagnoses have been excluded from existing models. Perhaps the most serious omission from hierarchical models of mental illness are the eating disorders, which are associated with the highest mortality rate of any class of psychiatric disorders. The long-term objective of this project is to to expand previously proposed models of mental illness, with a specific focus on eating disorders. The Specific Aims are to (1) determine where anorexic and bulimic syndromes fit into extant hierarchical models of mental illness, (2) expand extant models of mental illness by including a greater variety of Axis I and II disorders, in order to facilitate the correct placement of eating disorders within the hierarchy, and (3) examine the dispositional factors that are shared between eating disorder symptoms and other psychopathological symptoms in order to replicate and extend structural models at the syndrome- level. If the newly included disorders do not fit cleanly into extant models, this research will result in a revised hierarchical model of mental disorders relevant to the DSM. This investigation will be conducted in two phases. Phase 1 will consist of a retrospective analysis of participants from the National Comorbidity Survey - Replication (N=5,692) and will address Specific Aims 1 and 2. Phase 2 represents a novel study that will be conducted in a large student sample (N=400) recruited from the University of Iowa and will address Specific Aim 3. The proposed set of studies will be the first to include eating disorders among hierarchical models of mental illness. Taken together, the large nationally representative dataset in combination with symptom-level data has the potential to increase our understanding of the topography and etiology of eating and related disorders. In particular, the inclusion of additional disorders could lead to increased diagnostic validity of DSM categories and subtypes and may contribute to molecular and behavior genetic studies of eating disorders, particularly if heritable factors include susceptibility to other forms of mental illness. Thus, this line of research will lead to a more comprehensive empirically based system of psychopathology relevant to the DSM classification of disorders.